Detection of holes in a workpiece

ABSTRACT

A METHOD AND APPARATUS FOR DETECTING THE PRESENCE OF A RELATIVELY SMALL HOLE IN A WORKPIECE, SUCH AS A BULLET CASING, BY PASSING A SLENDER DETECT PIN THROUGH THE HOLE, IF THE HOLE IS OBSTRUCTED OR NON-EXISTENT, THE PINS ABUTS THE WORKPIECE WHICH TERMINATES, PREMATURELY, ADVANCEMENT OF THE PIN. A SENSING DEVICE IS PROVIDED AND IS RESPONSIVE TO PREMATURE TERMINATION OF THE PIN ADVANCEMENT TO CONTROL A MACHINE PERFORMING VARIOUS OPERATIONS ON THE MEMBER. ABSENCE OF THE HOLE IN THE MEMBER IS EMPLOYED TO STOP THE MACHINE AND ENABLES THE DEFECTIVE WORKPIECE TO BE REMOVED. ADDITIONALLY, THE DEVICE INCLUDES A SAFETY FEATURE BY WHICH, IN THE EVENT THAT THE SLENDER, FRAGILE PIN BREAKS, THE BREAKAGE WILL BE SENSED ALSO TO STOP THE MACHINE. THIS ENABLES THE BROKEN PIN TO BE REPLACED AND INSURES THAT THE DAMAGED PIN WILL NOT PERMIT ANY DEFECTIVE WORKPIECE HAVING NO HOLE TO PASS THROUGH THE DETECTING STATION TO SUBSEQUENT OPERATING STATIONS IN THE MACHINE.

NOV. 9, 1971 JULIEN DETECTION OF HOLES IN A WORKPIECE 2 Sheets-Shoat 1Filed June 5, 1970 7 FIG. 2

INVENTOR- DENIS JULIEN Nov. 9, 1971 D. JULIEN DETECTION OF HOLES IN AWORKPIECE 2 Sheets-ShegtE Filed June 5, 1970 INVENTOR DENIS JULIENlllQlllllillllll Illllllilll'lllil'l'1lllll' FIIIIIIl'lllliiliflllfi'"52044. ATTORNEYS United States Patent 3,618,396 DETECTION OF HOLES IN AWORKPIECE Denis Julien, Limoliou, Quebec, Canada, assignor to ValcartierIndustries, Inc., Courcelette, Quebec, Canada Filed June 3, 1970, Ser.No. 42,956 Int. Cl. 1507c 5/00 U.S. Cl. 73-432 13 Claims ABSTRACT OF THEDISCLOSURE A method and apparatus for detecting the presence of arelatively small hole in a workpiece, such as a bullet casing, bypassing a slender detect pin through the hole. If the hole is obstructedor non-existent, the pin abuts the workpiece which terminates,prematurely, advancement of the pin. A sensing device is provided and isresponsive to premature termination of the pin advancement to control amachine performing various operations on the member. Absence of the holein the member is employed to stop the machine and enables the defectiveworkpiece to be removed. Additionally, the device includes a safetyfeature by which, in the event that the slender, fragile pin breaks, thebreakage will be sensed also to stop the machine. This enables thebroken pin to be replaced and insures that the damaged pin will notpermit any defective workpiece having no hole to pass through thedetecting station to subsequent operating stations in the machine.

BACKGROUND OF THE INVENTION This invention relates to a method andapparatus for detecting the presence of a hole in a workpiece and, moreparticularly, to a technique employed in quality control for the massproduction of bullet cartridge casings.

An essential part of a conventional bullet casing is the fire hole,located in the rear end of the casing, which communicates the maincharge with the primer cap at the rear end of the casing. In the finallyassembled cartridge, the fire hole must be clear in order for thecartridge to function properly. Such cartridges are manufactured inmulti-station machines which perform a variety of operations on thecasing such as to punch the fire hole in the casing, check the presenceof the punched hole, debur the hole, and insert and seal the primer capinto the rear end of the casing. This invention relates to an improvedtechnique for detecting the presence or absence of the punched firehole.

Currently employed techniques for checking the presence of the fire holeinclude the use of a probe having a slender, needle-like pin which ispassed through the hole of the casing. If the fire hole is present, themovement of the probe is uninterrupted during its insertion into andretraction from the fire hole. If the casing does not have a fire holeor if the fire hole is obstructed, the advancement of the probe isinterrupted prematurely. The premature interruption is sensed by anappropriate switch which, in turn, controls the machines circuitry toshut the machine off. The defective casing then is removed.

Because the fire holes are relatively small, the probes also are smalland may tend to break, thus rendering the device ineffective indetecting the fire hole. This, in turn, permits defective casings havingno fire hole to pass through the detection station to the subsequentoperating stations in the machine.

This invention provides a detection device which not only causes themachine to stop when a defective cartridge is detected but which alsocauses the machine to stop if the detection probe or pin itself breaksor becomes damaged.

Patented Nov. 9, 1971 SUMMARY OF THE INVENTION The device is mounted inthe multi-station machine at a detect station. The machine includes across head which is movable heightwise toward and away from the casingssupported on a conveyor below. The casings are supported in a verticalattitude on the conveyor which transports the casings past the variousoperating stations in sequence. The various operating devices, includingthe detection device, are mounted to the cross head and move downwardlytoward the casings in a gang-like manner to perform their variousoperations in unison on the series of cartridges located below the crosshead.

In brief, the detection device includes a slender, downwardly projectingprobe which moves in unison, vertically, with the cross head. The probeadditionally is mounted for vertical movement in relation to the crosshead. Vertical movement of the probe in relation to the cross headactuates a switch which controls the chain to shut it off. Thus, when acasing having a fire hole is positioned below the probe, the pin of theprobe will pass freely through the hole and then will be retractedupwardly in unison with the cross head. There is no relative movement ofthe probe in relation to the cross head. If, however, the casing doesnot have a properly formed fire hole, the downward advancement of theprobe will be terminated prematurely when it abuts the casing. The crosshead, however, continues its downward movement, thus effecting therelative heightwise movement of the probe and cross head which, in turn,shuts the machine off.

In the event that the slender pin becomes broken, the detection deviceincludes an expandable element which extends downwardly of the brokenpin immediately after and in response to breakage of the pin. Whenexpanded, this element projects downwardly from the probe a distancesufficient so that when the probe and cross-head are urged downwardlytoward the casing, the lower end of the expanded element will engage thecasing prematurely. Continued downward movement of the cross-head willactuate the sensing mechanism and stop the machine. The operator thenmay replace the broken probe.

It is among the primary objects of the invention to provide an improvedfire hole detection technique which reduces the likelihood of failure todetect a defective cartridge.

A further object of the invention is to provide an improved fire holedetection method and apparatus which senses the existence of the firehole and also detects malfunction of the detection device.

Still another object of the invention is to provide a method andapparatus for sensing the presence of a fire hole in a cartridge casingwhich is effective to shut off the machine in response to the presenceof a defective cartridge casing or a defect in the detection deviceitself.

DESCRIPTION OF THE DRAWINGS These and other objects and advantages ofthe invention will be understood more fully from the following detaileddescription thereof, with reference to the accompanying drawingswherein:

FIG. 1 is a sectional elevation of the detection device as mounted tothe cross head of the multi-station machine;

FIG. 2 illustrates the operation of the device when testing a properlyformed cartridge;

FIG. 3 illustrates operation of the device testing the cartridge havingno fire hole;

FIG. 4 is an illustration of the device in which the detection pin hasbeen broken and which illustrates the manner in 'which the deviceactuates the control circuit in response to breakage of the pin; and

FIG. is a sectional view through the detection pin as seen from theplane 55 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT A shown in FIG. 1, the detectiondevice is mounted to the cross head of the machine. The cross head 10 islocated directly above a conveyor 11 (see FIG. 2) which supports thecartridges for advancement below the cross head 10, so that thecartridges on the conveyor may be presented, sequentially, to thevarious operating devices mounted to the cross head 10. The conveyor 11may include a plurality of cartridge supporting posts 13 which supportthe cartridge 15 in a vertical attitude with the head of the cartridgefacing upwardly. In the illustrative embodiment the cartridge includes arecess 17 in the head to receive the primer cap (not shown). The firehole 19 is formed in the cartridge head and communicates the recess 17with the interior of the cartridge 15. The detection device includes acylindrical probe body 12 which is supported by the cross head 10 forvertical, sliding movement within the hole 14 formed in the cross head.The lower end of the probe body is formed to define an enlarged collarportion 16 which also defines the shoulder 18. A top retaining ring 20surrounds the probe body 12 and rests on the shoulder 18. The ring 20 isfastened to this position by a set screw 22.

The probe body 12 is biased in the most downward position shown in FIGS.1 and 2 by means of a coil spring 24 which surrounds the lower end ofthe probe body and extends between the underside of the cross head 10and the upper surface of the top retaining ring 20.

The heightwise position of the probe in relation to the cross head isadjustable by means of a nut 26 which is threaded about the upper end ofthe probe body 12, and which rests on the upper surface of the crosshead 10.

The upper end of the probe body also includes an upwardly extendingmicroswitch trip member 28 which may have a conical surface formed aboutits upper end. The microswitch trip member 28 has a lower shank 30 whichis threaded into a hole formed in the upper end of the probe body 12 topermit the relative height between the trip member 28 and probe body 12to be adjusted. Once adjusted to the desired relative height, the tripmember 28 is locked in position by the lock nut 32.

The detection device also includes a microswitch 34 which is mountedsecurely to the cross head 10 for actuation by upward movement of theprobe body 12 and trip member 28 in relation to the cross head 10. Asdescribed below, the microswitch 34 is incorporated into the circuit ofthe machine to shut the machine off when actuated.

The lower end of the probe body 12 receives and supports the detectionpin 36. The pin 36 is received and secured within a central bore 38formed in the probe housing 12 by the set screw 40. The lower,downwardly projecting tip of the detection pin 36 is tapered to aslender shape which may be passed through the fire hole 19 in the casing15 being tested.

In operation, the cartridge casing 15, as shown in FIG. 2, is positionedby the conveyor directly below the detection device with the head end ofthe casing 15 facing upwardly toward the detection device. The crosshead 10 then is moved downwardly to advance the various operatingdevices, including the detection device, downwardly toward and intoengagement with their respective cartridge casings supported below. Ifthe fire hole 19 is formed properly in the casing 15, the slender, lowerend of the detection pin 36 will pass freely into and through the firehole 19. The cross head 10 then is raised upwardly to the idle positionto enable the conveyor to advance one operating station, thus presentingeach cartridge on the conveyor to the next operating station in themachine. Thus, when the fire hole 10 is formed properly within itscartridge casing 15, the cross head 10, detection device and microswitch34 move in unison. There is no relative .4 heightwise movement of theprobe body 12 to the cross head 10 and the microswitch 34 thus remainsunactuated.

If, however, as shown in FIG. 3, the cartridge casing 15 did not have aproperly formed fire hole 19, then the lower end of the detection pin 36would abut the head end of the cartridge casing thus terminatingprematurely the downward movement of the probe body 12. The cross head10 and microswitch 34, however, would continue to advance downwardly inrelation to the stationary probe body 14 and microswitch trip 28. Thisactuates the microswitch 34, which, in turn, stops operation of themachine and enables the defective cartridge to be removed.

As mentioned above, because of the relatively slender and fragileconstruction of the lower end of the detection pin 36, it is notuncommon for the detection pin to break, as when subjected to excessiveshear or compressive stresses. In order to obtain the high degree ofquality control necessary in fabricating bullets, any such mulfunctionof the detection device should be corrected immediately so that nodefective casings are passed to subsequent operating stations. Inaccordance with the invention, the lower end of the detection deviceincludes an arrangement by which breakage of the lower end of thedetection pin 36 will result in actuation of the microswitch 34 thusshutting off the machine.

As shown in FIGS. 1 and 4, the safety arrangement for detecting pinbreakage includes a detection pin bushing 46 which is retained,slideably, within an enlarged concentric bore 48 formed at the bottom ofthe probe body 12. The bushing 46 has a longitudinal hole formedtherethrough which receives the lower end of the detection pin 36. Abottom retaining ring 50 having an upturned peripheral flange 52 islocated at the underside of the probe body 12. The retaining ring 50 hasa central hole which registers with the enlarged bore 48 and whichreceives the lower end of the detection pin bushing 46. The lower end ofthe detection pin bushing which projects downwardly beyond the bottomretaining ring 50 has a shoulder 54 formed thereon which receives andgrips the retaining ring 50 between it and the bottom surface of theprobe body 12. These parts are maintained in this arrangement by meansof a cotter pin 56 which is passed through a transverse hole 58 formedin the lower, protruding end of the detection pin 36. A relatively heavycompression spring 60 is provided which surrounds the collar portion 16ofthe probe body 12 and which bears against the underside of the topretaining ring 20 and the upper surface of the bottom retaining ring 50.When the device is assembled in the configuration shown in FIG. 1, thespring 60 is in a compressed state so that if the cotter pin 56 isreleased (as when the lower tip of the detection pin 36 ruptures) thespring 60 will expand and will drive the bottom retaining ring 50 andthe bushing 46 downwardly to the position shown in FIG. 4.

The extent of downward movement of the bottom retaining ring 50 anddetection pin bushing 46 is limited by a slot 62 formed along one sideof the bushing 46. A stop screw 64 is threaded transversely through thecollar portion 16 of the probe body 12 and protrudes into the slot 62,thus limiting the extent of downward movement of the bushing 46 when theupper end of the slot 62 engages the inner end of the stop screw 64. Thebushing 46 is precluded from rotating within its receptive bore 4'8 bymeans of a flat 66 formed on the opposite side of the bushing whichcooperates with the set screw 68 threaded through the collar portion 16of the probe body 12' and which bears lightly against the fiat 66.

FIG. 4 shows the configuration of the device when the lower end of thedetect pin 36 has been broken and the cotter pin 56 is released from itslocking position. Once the cotter pin 56 has been released thecompression spring 60 forces the bottom retaining ring 50 and bushing 46to expand downwardly until the upper end of the slot 62 engages the stopscrew 64. This effectively extends the lower surface of the bushing 46in relation to the probe to the level at which the lower tip of thedetection pin extended.

When the broken detection device is urged downwardly toward a cartridgecasing, as shown in FIG. 4, the expanded broad bottom surface of thedetection pin bushing 46 will abut the end of the casing before thecross head has reached the full downward limit of its travel. Withdownward advancement of the probe body 12 thus interrupted, continueddownward advanmement of the cross head 10 causes the microswitch 34 toengage the micro-v switch trip member 28 on the probe body 12. and stopthe machine.

Because of the relatively small dimensions of the fire hole 19 and thecorrespondingly small dimensions of the tapered lower tip of thedetection pin 36, it is important that these elements be in registrybefore the cross head 10 brings the detection device downwardly towardand into engagement with the cartridge casing. If the tip of thedetection pin 36 is bent or is otherwise deformed so that it cannot passfreely into and out of the fire hole it is essential that this conditionbe corrected immediately in order to insure that defective casings arenot passed through to the following stations in the machine. In theinstant invention, this is accomplished by providing a weak portion inthe lower end of the detection pin 36 which will fracture when anyabnormal load is imposed on it. This weakened region is provided by therelatively thin sidewalls 70 which are defined by the transverse hole 58in the detection pin 36 through which the cotter pin 56 is passed. Thedetection pin 36 will rupture at the weakened sidewalls 70 in responseto excessive loads. As described above, this releases the cotter pin '56and permits the bottom retaining ring 50 and bushing 46 to expanddownwardly under the force of the spring 60. This, in turn, causespremature termination of downward movement of the probe which triggersthe microswitch 34 as described above.

It should be understood that the foregoing description is intendedmerely to be illustrative of the invention and that other embodimentsand modifications thereof may be apparent to those skilled in the artwithout departing from its spirit. For example, although the inventionhas been described as being useful primarily in connection with thetesting and detection of fire holes formed in bullet cartridges, it maybe employed with equal efiectiveness in almost any environment which itis desirable to check the presence or accurate formation of a holeformed in a workpiece, particularly when the hole is relatively small.Furthermore, although the invention is particularly useful inmulti-station 'machines which perform a number of operations on a workpiece, it may be employed as a single station device if desired.

Having thus described the invention, what is claimed is:

1 A device for detecting the presence of a hole in a workpiececomprising:

a probe unit having a pin dimensioned to be passed through said hole;

means for supporting said workpiece in predetermined position inrelation to said probe unit; means mounting said probe unit for movementalong a path that is toward and away from said supported workpiece andin a stroke such that said probe may pass through said hole and then beretracted out of said hole, said portion of said stroke that is towardsaid member being terminable, prematurely, by engagement of said pinwith a member having no hole;

means responsive to said premature termination of advancement of saidprobe unit for signalling the absence of said sole in said member; and

means responsive to breakage of said pin for eifecting prematuretermination of advancement of said probe unit.

2. A device as defined in claim 1 wherein said means mounting said probeunit for said movement comprises:

a support member disposed above and movable toward and away from saidsupported workpiece whereby said probe may be advanced toward and awayfrom said workpiece in unison with said support member; means mountingsaid probe to said support member for height-wise movement in relationthereto whereby when said advancement of said probe is terminatedprematurely, said support member may continue and complete its downwardstroke; and said means responsive to said premature termination ofadvancement of said probe unit comprising means responsive to saidrelative heightwise movement of said probe and support means.

3. An apparatus as defined in claim 2 wherein said means responsive tosaid pin breakage for effecting said premature termination of probeadvancement comprises:

means for expanding the efiective length of said probe in response tosaid pin breakage.

4. An apparatus as defined in claim 3 wherein said probe unit comprises:

a probe body mounted to said probe support member for said heightwisemovement in relation thereto;

a detection pin mounted to said probe body and having a lower endprojecting downwardly from said probe body;

said means for expanding the effective length of said probe comprising:

a bushing slideably mounted to the lower end of said probe body formovement along and axially of said pin, said pin passing through saidbushmeans biasing said bushing in a downward direction; and

means releasably restraining said downward movement of said bushing sothat when released, said bias means will urge said bushing downwardly inrelation to said probe body to expand the effective length thereof.

5. An apparatus as defined in claim 4 wherein said means for releasablyrestraining said downward movement of said bushing comprises:

a transverse pin passing through a hole formed in the lower end of theprobe pin, the bottom end of said bushing bearing downwardly againstsaid transverse p111.

6. An apparatus as defined in claim 5 wherein the wall defined by saidhole is relatively weak whereby any excessive stresses imposed on saidpin will cause said pin to rupture about said hole thereby releasingsaid transverse pm.

7 An apparatus as defined in claim 4 wherein said means biasing saidbushing in a downward direction comprises:

an upper retaining ring secured to and about the probe body;

a lower retaining ring at the bottom of said probe body and having acentral hole formed therein, said bushing extending downwardly throughsaid central hole and said lower retaining ring, said bushing having ashoulder to support said lower retaining ring; and

a compression spring extending between the upper and lower retainingrings.

8. An apparatus as defined in claim 7 wherein said means for restrainingsaid downward movement of said bushing comprises:

a transverse pin passing through a hole formed in the lower end of saidprobe pin, the lower end of said bushing bearing downwardly against saidtransverse pin.

9. An apparatus as defined in claim 4 further comprising:

means limiting the extent of downward movement of said bushing inrelation to said probe body.

10. An apparatus as defined in claim 9 wherein said means limiting saiddownward movement of said bushing comprises:

a slot formed along the length of said bushing; and

a stop member secured to said probe body and extending into said slotwhereby engagement of the ends of said slot with said stop member limitsthe extremities of movement of said bushing.

11. An apparatus as defined in claim 10 further comprising:

means precluding rotation of said bushing about-its longitudinal axisaxis including a flat formed on and along the side of said bushing and aguide member secured to said probe body and extending inwardly towardsaid fiat, said guide bearing slideably against said fiat.

12. A method for detecting the presence of a hole in a workpiececomprising:

providing a probe having a slender pin extending therefrom;

advancing said probe toward said member so that when said member has ahole formed therein, said probe will pass through said hole to apredetermined extent;

retracting said probe and said pin thereof from said hole;

whereby in the event said member does not include said hole saidadvancement of said probe toward said member will be terminatedprematurely;

signalling the absence of said hole in response to said prematuretermination of advancement of said probe; and

etfecting an identical signal in response to breakage of said pinportion of said probe.

13. A method as defined in claim 12 wherein said step of effecting saidsignal in response to breakage of said probe comprises:

expanding the effective length of said probe along the direction ofadvancement thereof toward said workpiece whereby advancement of saidprobe having a broken pin will be terminated prematurely by reason ofengagement of the expanded portion of said probe with said workpiece.

References Cited UNITED STATES PATENTS S. CLEMENT SWISHER, PrimaryExaminer US. Cl. X.R. 20988

